U.S. patent number 8,320,902 [Application Number 12/942,798] was granted by the patent office on 2012-11-27 for system and method for selecting services in a wireless communication network.
This patent grant is currently assigned to Kapsch Trafficcom AG. Invention is credited to Dmitri Khijniak, Justin Paul McNew, John Thomas Moring.
United States Patent |
8,320,902 |
Moring , et al. |
November 27, 2012 |
System and method for selecting services in a wireless
communication network
Abstract
A system and method for selecting a preferred connection point
from a choice of one or more available connection points in a
wireless communication network. The system and method include:
determining a link quality for the one or more available connection
points; establishing a connection to a first connection point when
there is no existing established connection, the first connection
point offers a desired service, and the link quality for the first
connection point exceeds a first threshold value, wherein a service
priority is considered in determining the link quality of the first
connection point; maintaining the established connection to the
first connection point when the link quality exceeds a second
threshold value; and making eligible the established connection to
the first connection point for preemption by a second connection
point, when the link quality for the first connection point is less
than the second threshold value.
Inventors: |
Moring; John Thomas (Encinitas,
CA), Khijniak; Dmitri (San Diego, CA), McNew; Justin
Paul (Studio City, CA) |
Assignee: |
Kapsch Trafficcom AG (Vienna,
AT)
|
Family
ID: |
44764072 |
Appl.
No.: |
12/942,798 |
Filed: |
November 9, 2010 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
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US 20120115417 A1 |
May 10, 2012 |
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Current U.S.
Class: |
455/422.1;
455/432.3 |
Current CPC
Class: |
H04W
48/20 (20130101); H04W 48/08 (20130101) |
Current International
Class: |
H04W
4/00 (20090101) |
Field of
Search: |
;455/41.2,422.1,429,432.3,435.2,435.3,465-466 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Extended European Search Report for corresponding European
Application No. 11 450 124.0, dated Feb. 21, 2012, 13pp. cited by
other .
Office communication issued on May 16, 2012 in corresponding
European Patent Application No. 11 450 124.0, 9pp. cited by
other.
|
Primary Examiner: Maung; Nay A
Assistant Examiner: Perez; Angelica
Attorney, Agent or Firm: Christie, Parker & Hale,
LLP.
Claims
What is claimed is:
1. A method for connecting a mobile unit to a preferred connection
point from a choice of one or more available connection points in a
wireless communication network, the method comprising: determining
a link quality between the mobile unit and the one or more
available connection points; establishing a connection between the
mobile unit and a first connection point when there is no existing
established connection, the first connection point offers a desired
information service, and the link quality for the first connection
point exceeds a first threshold value, wherein an information
service priority is considered in determining the link quality of
the first connection point; maintaining the established connection
to the first connection point when the link quality exceeds a
second threshold value, which is larger than the first threshold
value; and making eligible the established connection to the first
connection point for preemption by a second connection point, when
the link quality for the first connection point is less than the
second threshold value, wherein the first connection point is
preempted by the second connection point when the second connection
point offers at least one desired information service, the link
quality for the second connection point exceeds the first
threshold, and the difference between the link quality of the
established connection to the first connection point and the link
quality of the second connection point exceeds a fourth threshold
value.
2. The method of claim 1, further comprising abandoning the
established connection to the first connection point when the link
quality for the first connection point is less than a third
threshold value.
3. The method of claim 1, wherein the service priority is
determined by information delivered by a service provider over the
wireless communication network.
4. The method of claim 1, wherein determining the link quality is
based on received signal strength.
5. The method of claim 4, wherein the received signal strength is
time-averaged.
6. The method of claim 5, wherein a weighting factor is used for
the signal strength time-average.
7. The method of claim 1, wherein establishing a connection to the
first connection point includes considering a time duration since a
previous change of connection.
8. The method of claim 7, wherein the previous change of connection
is one or more of the group consisting of a connection
establishment, a connection preemption, and a connection
abandonment.
9. The method of claim 3, wherein preempting the first connection
point includes considering a time duration since a previous change
of connection.
10. The method of claim 9, wherein the previous change of
connection is one or more of the group consisting of a connection
establishment, a connection preemption, and a connection
abandonment.
11. The system of claim 1, wherein the service priority is
determined by information delivered by a service provider over the
wireless communication network.
12. The method of claim 2, wherein any one of the first, second, or
third thresholds is dynamically adjusted.
13. A system for selecting a preferred connection point from a
choice of one or more available connection points in a wireless
communication network comprising: means for determining a link
quality between a mobile unit and the one or more available
connection points; means for establishing a connection between the
mobile unit and a first connection point when there is no existing
established connection, the first connection point offers a desired
information service, and the link quality for the first connection
point exceeds a first threshold value wherein an information
service priority is considered in determining the link quality of
the first connection point; means for maintaining the established
connection to the first connection point when the link quality
exceeds a second threshold value, which is larger than the first
threshold value; and means for making eligible the established
connection to the first connection point for preemption by a second
connection point, when the link quality for the first connection
point is less than the second threshold value, wherein the first
connection point is preempted by the second connection point when
the second connection point offers at least one desired information
service, the link quality for the second connection point exceeds
the first threshold, and the difference between the link quality of
the established connection to the first connection point and the
link quality of the second connection point exceeds a fourth
threshold value.
14. The system of claim 13, further comprising means for abandoning
the established connection to the first connection point when the
link quality for the first connection point is less than a third
threshold value.
15. The system of claim 13, wherein determining the link quality is
based on received signal strength.
16. The system of claim 15, wherein the received signal strength is
time-averaged.
17. The system of claim 16, wherein a weighting factor is used for
the signal strength time-average.
18. The system of claim 13, wherein the service priority is
determined by information delivered by a service provider over the
wireless communication network.
Description
FIELD OF INVENTION
The present invention relates generally to the field of mobile
communications, and more particularly, to system and method for
selecting services in a communication network.
BACKGROUND
Certain wireless communications systems, such as the Wireless
Access in Vehicular Environments (WAVE) system defined by IEEE 1609
family of standards, are comprised of mobile vehicular units and
roadside radio access units allowing connectivity into a network
infrastructure. The units of these systems exchange both high
priority/low latency data (e.g., emergency warnings), and low
priority/best effort data (e.g., map updates). They employ a series
of radio channels in the 5 GHz band, although operation in other
frequency bands is also possible.
Applications, running within a vehicle or mobile host, access
applications or services running on network hosts coupled to the
wireline network. This is accomplished via a wireless link from the
mobile host through a roadside radio connection or access device,
and associated network links from the radio connection device
through the network to the network host. Mobile hosts may connect
through multiple radio connection devices in sequence, experiencing
interruptions in connectivity while in between wireless coverage
areas.
The mobile environment offers unique challenges for applications,
including the following. With relatively short range communications
(e.g., 1000 m), the mobile host's communication zone is limited and
its communication opportunities can be short lived. For mobile
applications, the time duration of the connection is critical.
Thus, the sooner the mobile application can establish/reestablish
its session after reaching an area of coverage, the longer the
application has to exchange useful data. Link quality is also
paramount. It may be advantageous for a mobile device to abandon
connectivity with a roadside device in order to connect to another
device through a higher quality link. In addition to link quality,
it may be advantageous for a mobile device to consider the range of
services being offered by a roadside device when deciding where to
make its connection. Once a connection session to the first
roadside device is established, a mobile device is communicating to
the first roadside device for the duration of the connection
session. During that time, mobile application cannot establish a
simultaneous communication session with another roadside device.
While the mobile device is communicating to one roadside device, it
can still collect link quality characteristics of other nearby
roadside devices. The mobile application has to terminate the first
connection session in order to establish the connection session to
the second device.
In conventional implementations, decisions are made on the basis
of, first, whether a connection point is available, and second,
whether it offers a service of interest to the mobile unit. Upon
making connection, the connection is held as long as possible, for
example, until the mobile unit moves out of range.
This results in at least two problems. The first problem is that
connections might be attempted before adequate link quality is
achieved, resulting in marginal or intermittent connectivity. The
second problem is that once a connection is made, no attempt is
made to recognize a more advantageous connection point that might
become available.
Therefore, there is a need for a system and method that allows the
mobile device to choose an optimal connection point when multiple
connection points are available. There is also a need to mitigate
the problem of attempting marginal connections.
While sharing some characteristics with cellular communication
systems, the WAVE is distinct in several ways. First, a cellular
system is intended to provide wide area coverage. The WAVE system
uses short range communication links and often provides
discontinuous "hot spot" coverage in local areas. Second, each
cellular base offers a homogenous set of services (voice, short
messaging, etc.); selection of the connection point is not made
based on service offering. A WAVE connection point may offer a
single specialized service (e.g., parking services) or a selection
of services. Whereas a cellular system is engineered to minimize
the overlap between adjacent coverage areas, multiple WAVE
connection point, each offering its own set of services, may be
located in close proximity. An example would be two parking
services, each operated by a garage on each side of the street.
A cellular handset prefers to always remain in connection with the
cellular network. A mobile WAVE device would prefer to be in an
unconnected state where it can scan for potentially interesting
services, rather than remain connected to a connection point that
does not offer information of value.
These differences call for a different set of service selection
methods for WAVE than have been used in cellular systems. When
choosing among multiple possible cellular connections (between a
handset and one of multiple base stations), the selection criteria
are link quality and base station loading. Type of service is not a
criterion, since base stations within a carrier's network generally
offer similar services. When choosing among multiple possible WAVE
connections, the selection criteria used by the invention disclosed
herein are, first, services offered, and then link quality. A
connection point with an uninteresting service will not be
accessed, regardless of a good link quality. Likewise a connection
point with a poorer link quality but more interesting set of
services would be chosen over a connection point with better link
quality but less interesting services.
SUMMARY OF THE INVENTION
In some embodiments, the present invention is a system and method
for selecting a preferred connection point from a choice of one or
more available connection points in a wireless communication
network. The system and method include: determining a link quality
for the one or more available connection points; establishing a
connection to a first connection point when there is no existing
established connection, the first connection point offers a desired
service, and the link quality for the first connection point
exceeds a first threshold value, wherein a service priority is
considered in determining the link quality of the first connection
point; maintaining the established connection to the first
connection point when the link quality exceeds a second threshold
value; and making eligible the established connection to the first
connection point for preemption by a second connection point, when
the link quality for the first connection point is less than the
second threshold value.
The established connection to the first connection point may be
abandoned when the link quality for the first connection point is
less than a third threshold value.
Furthermore, the first connection point may be preempted by the
second connection point according to a fourth threshold value,
which is a differential between the link quality of the established
connection to the first connection point and the link quality of
the second connection point.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates vehicles moving along a roadway, passing
roadside antenna units at intervals, according to some embodiments
of the present invention.
FIG. 2 shows an exemplary state diagram, according to some
embodiments of the present invention.
FIGS. 3A and 3B depict an exemplary simplified decision threshold
graph according to some embodiments of the present invention.
FIGS. 4A and 4B show an extended exemplary decision threshold graph
according to some embodiments of the present invention.
FIG. 5 shows an exemplary intersection with overlapping zones of
coverage, according to some embodiments of the present
invention.
FIG. 6. shows a process flow diagram, according to the prior
art.
FIG. 7. shows an exemplary process flow diagram, according to some
embodiments of the present invention.
DETAILED DESCRIPTION
In some embodiments, the present invention is a method and system
for selecting a preferred connection point from a choice of one or
more available connection points in a wireless communication
network based on whether the connection point provides the desired
service and the link quality.
FIG. 1 illustrates vehicles moving along a roadway, passing
roadside antenna units at intervals, according to some embodiments
of the present invention. As shown, there may be multiple
connection options available at a given point in space and time. A
mobile unit desiring connectivity may not have enough resources
(e.g., radios) to connect to all connection points. The present
invention provides decision criteria for selecting the right
connection point(s) among the multiple connection points.
The decision includes 1) when to connect to a connection point from
an unconnected state, 2) when to change connection points, and 3)
when to disconnect. This is illustrated in FIG. 2 (explained in
more detail below), where each arrow between one of the two system
states ("Connected" and "Unconnected") represents one of the
decisions. The primary criteria used are the services offered by
the connection point and the quality of the link between the
connection point and the mobile unit. Link quality may be simply
estimated in a radio environment through monitoring received signal
strength over time, however, any link quality metric may be used
without altering the nature of the invention.
The invention also accounts for priorities that may be assigned to
different connection points. This accounts for the possibility that
the different connection points may have aspects that are more or
less appealing to the mobile unit. For example, one connection
point may offer a more up-to-date information service than another,
making it more desirable (assuming adequate link quality).
FIGS. 3A and 3B depict an exemplary simplified decision threshold
graph according to some embodiments of the present invention.
Consider the simplified decision threshold graph shown in FIG. 3A.
As shown, Link Quality is charted on the vertical axis, normalized
from 0 (minimum) to 100 (maximum); time is charted on the
horizontal. Two Link Quality thresholds are identified. Connect
Threshold is the Link Quality value above which a connection is
established. Disconnect Threshold is the Link Quality value below
which an established connection is abandoned. Thus Link Qualities
in the double-shaded zone always result in connections; Link
Qualities in the single-shaded zone result in connections only if
they have already been established. A connection in the
double-shaded zone is considered good. A connection in the
single-shaded zone is of reduced quality and in danger of being
lost. In the unshaded zone, there are no connections due to poor
Link Quality.
FIG. 3B shows an example of changing Link Quality over time, with
connection decisions made according to the simplified decision
threshold graph. The dark line shows the varying link quality
between the connection point and the mobile unit over time. At
point A, the connection point is recognized and determined to be of
interest, but the Link Quality is not adequate for connection
(i.e., does not exceed the Connect Threshold). Even at point B, the
Connect Threshold is not reached, as a result, no action is taken.
However, at point C, the Link Quality surpasses the Connect
Threshold, accordingly, a connection is made. The connection is
retained through point D, when the Link Quality falls below the
Connect Threshold, all the way to point E, when the Link Quality
goes below the Disconnect Threshold, at which time the connection
is abandoned. The hysteresis between the Connect Threshold and
Disconnect Threshold prevents rapid toggling of connections under
marginal link conditions. Appropriate values for the thresholds may
be determined analytically or through experiment. For example, if
the nominal sensitivity of the receiver is -85 dBm, the Connect
Threshold might be set to around -75 dBm to ensure a strong
connection, and the Disconnect Threshold might be set to about -85
dBm.
Threshold values can also be controlled dynamically. For example,
in a rural zone where RSE density is low, connect threshold values
can be lowered and thus making OBU more sensitive to RSE
information. Similarly, in an urban area, where RSE density is
higher, the threshold values can be increased thus making OBU less
receptive to weaker signals. Moreover, the threshold values may be
calculated by the mobile unit based on its own capabilities or its
knowledge of its environment; the values could be calculated off
line and configured into the mobile units; or the values could be
calculated by a stationary unit considering the local environment
or the capabilities of the mobile unit and delivered to the mobile
units via the communications link. Furthermore, the threshold
values can be determined by the mobile unit to meet user
configuration preferences, performance targets, application needs,
or weather conditions.
FIGS. 3A and 3B only account for the presence of a single
connection point. In some cases, it is desirable to preempt the
current connection by switching to another connection with higher
Link Quality (or with preferable services). Once again, though, it
is undesirable for a mobile device to experience multiple
unnecessary and disruptive switches between connection points.
FIGS. 4A and 4B show an extended exemplary decision threshold graph
according to some embodiments of the present invention. FIG. 4A
illustrates how the invention accounts for the presence of multiple
connection points, in some embodiments. A Stay Threshold is added.
When a connection's Link Quality exceeds the Stay Threshold (i.e.,
is in the densely shaded zone), the connection is considered to be
excellent and may not be preempted by another connection. A
connection with Link Quality below the Stay Threshold (i.e., in the
double- or single-shade zone) is of good quality but is eligible
for preemption if a "better" connection option is available.
One more threshold is added to prevent a disruptively high number
of preemptions. The Switch Delta Threshold is the difference in
Link Quality required between two connections before preemption is
allowed.
As shown in FIG. 4B, a first connection (solid line) is established
at point A. A second connection option (dotted line) is recognized.
Between points A and C, the second connection does not preempt the
first connection, even though its Link Quality surpasses that of
the first connection at point B, because the Link Quality
differential does not exceed the Switch Delta Threshold. Between
points C and D, the Link Quality of the first connection exceeds
the Stay Threshold, making it ineligible for preemption, regardless
of the second Link Quality. At point E however, the first Link
Quality is less than the Stay Threshold, and the second Link
Quality exceeds the first by the Switch Delta Threshold, so the
second connection preempts the first. At point F, the first Link
Quality again exceeds the second, but not by the Switch Delta
Threshold, so no preemption occurs.
FIG. 5 shows an exemplary intersection with overlapping zones of
coverage, according to some embodiments of the present invention.
The figure also illustrates the utility of the present invention in
a WAVE scenario. As shown, the vehicle 51 is initially in zone 1,
i.e., where it can achieve a high quality connection with
connection point 1. It is approaching an intersection 52 where the
link to connection point 1 loses strength, and other connection
points become available. The vehicle does not abandon the first
connection until two conditions are met. First, its Link Quality
must not be excellent (i.e., fall below the Stay Threshold).
Second, the Link Quality associated with another connection point
must exceed that of the current connection by some margin (i.e.,
the Switch Delta Threshold). Although, WAVE systems are used in
this disclosure as an example, the invention is suitable for any
communication system that includes the capability of choosing among
multiple connection options.
According to some embodiments of the present invention, at some
point around the intersection, the vehicle preempts the connection
with connection point 1 and establishes a connection with
connection point 3, which supports coverage zone 3, without
knowledge of its own location or the location of the connection
points. According to some embodiments, the vehicle may preempt the
connection with connection point 1 and establish a connection with
connection point 3, using location data.
It is not desirable that the vehicle connects to the connection
points represented by either zone 2 or zone 4, since the vehicle
will quickly transit those zones. To prevent this, Link Quality may
include a time component. For example, a weighted average of the
latest N signal strength measurements could be used for the Link
Quality. Furthermore, the signal threshold may be dynamically
adjusted for optimal filtering.
An example of a weighted average would incorporate knowledge of N
recent link measurements, as shown below. The weighted Link Quality
L is the average of N products, each consisting of a weight W
multiplied by a measurement value M. In general, the more recent
measurements have higher weights, i.e.,
W.sub.A.gtoreq.W.sub.B.gtoreq. . . . .gtoreq.W.sub.N.
L=(W.sub.AM.sub.A+W.sub.BM.sub.B+ . . . +W.sub.NM.sub.N)/N (1)
Other weighting algorithms may be used. In some embodiments, the
present invention employs time delays as well as hysteresis
thresholds to prevent frequent changes in connectivity.
FIG. 2 shows an exemplary state diagram, according to some
embodiments of the present invention. Any pair of the change types
possible in FIG. 2 (Connect to Change, Change to Change, Change to
Disconnect, Connect to Disconnect, Disconnect to Connect) may have
a time parameter associated with it. If a time duration exceeding
the time parameter value has not elapsed since the first change,
then the second change is not allowed.
In some embodiments, different connection points may offer
different types of service, some or all of which having a different
priority. For example, one connection point might offer a weather
service; another might offer traffic; another might offer both. A
simple implementation would include a binary connection decision
(yes/no) for each connection point related to the presence of a
service of interest to the mobile. In some embodiments of the
present invention, a priority is assigned to each service, by the
system or by the user. For example, a user may indicate a desire
for parking and therefore any services related to parking will be
treated as higher priority service, compared to, for example,
weather services.
The nature of the service priority is not critical to the operation
of the invention, that is, different connections could have
different priorities based on the information exchanges available
through that connection point and perhaps the intrinsic state of
the device. For example, a connection point offering map data might
be of low interest to one mobile unit, but of high interest to
another unit whose map data is out of date or because of user
preferences established in the device. The presence of one or more
services of interest to the mobile increases the metric (now a
combined Link Quality and Priority metric) associated with a
connection point and compared to the various threshold levels in
making connect/disconnect/preempt decisions. The service priority
may be determined by information delivered by a service provider
over the wireless communication network.
FIG. 6. shows a process flow diagram, according to the prior art.
As shown in block 61, the process begins when a new connection
point is recognized. At this point, a decision is made to connect
in block 62. Once connected, no other connection points are
considered, until a loss of signal is experienced, in block 63. At
this point, the disconnect decision is made in block 64, and the
device reverts to monitoring the channel for a new connect point in
block 61.
FIG. 7 shows an exemplary process flow diagram, according to some
embodiments of the present invention. The exemplary process flow of
FIG. 7 is executed by one or more computers, for example, one or
more mobile units, one or more stationary units, and/or a central
processing unit. As shown, a link quality for the one or more
available connection points is determined and a connection to a
first connection point is established when there is no existing
established connection, and the link quality for the first
connection point exceeds a first threshold value. The established
connection to the first connection point is maintained while the
link quality exceeds a second threshold value. The established
connection to the first connection point is made/marked eligible
for preemption by a second connection point, when the link quality
for the first connection point is less than the second threshold
value.
As shown in FIG. 7, a new connect point is recognized in block 701.
The connection point is first evaluated to determine whether it
offers a preferred service 711; if not the connection point is
ignored. Otherwise, a check is made to see if a connection has
already been established in block 702. If no connection has been
established and the new connection point's link quality does not
exceed the Connect Threshold, the potential connection is not
accessed, as shown in block 704. However, if the new connection
point's link quality exceeds the Connect Threshold in block 703, a
connection is established in block 705.
If the new connection point is recognized in block 701 when a
connection already exists in block 702, then the existing
connection's link quality is compared to the Stay Threshold, as
shown in block 706. If the Stay Threshold is exceeded, the
potential connection is not acted upon in block 704. If the Stay
Threshold is not exceeded by the existing link, the potential
connection's link quality is compared to the Connect Threshold, and
also the difference between the potential connection's link quality
and the existing connection's link quality compared to the Switch
Delta Threshold in block 707. If both of these thresholds are
exceeded, the existing connection is terminated 708 and the new
connection is established in block 705.
Once a connection is established in block 705, the Disconnect
Threshold is monitored in block 709. If the link quality falls
below the Disconnect Threshold, the connection is terminated in
block 710. While the connection is in place, new potential
connections are monitored. This feature is not explicitly shown in
FIG. 7 due to the limitations of the flow diagram format in
representing parallel tasks.
It will be recognized by those skilled in the art that various
modifications may be made to the illustrated and other embodiments
of the invention described above, without departing from the broad
inventive scope thereof. It will be understood therefore that the
invention is not limited to the particular embodiments or
arrangements disclosed, but is rather intended to cover any
changes, adaptations or modifications which are within the scope
and spirit of the invention as defined by the appended claims.
* * * * *